MITOSIS

1
MITOSIS

• PAGE 72-77
• PAGE 76-77 - picture

2
Mitosis

• The process in which a cell duplicates its
  chromosomes and then splits in two
• Remember every cell (in the nucleolus) contains
  23 pairs of chromosomes
• Mitosis is a continuous cell cycle
• Cell cycle is growth and division that cells
  undergo

3
Phases of Mitosis(see handouts and p76-77)

• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• during these phases the nucleus divides and
  the cytoplasm also divides

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Interphase

• Preparation phase
• Before cell division very active phase
• Non dividing phase
• Stage between divisions
• Three things occur
• Cell grows to mature size cell doubles in size
• DNA is copied replication of DNA
• Prepares to divide
• Chromosomes are long and thin (chromatin-like)
• Exact copy of the chromosomes are made in the
  nucleus

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Prophase

• In animal cells (not in plant cells) 2 small
  cylinder shape structures begin to separate just
  outside the nucleus called centrioles
• In the nucleus the doubled chromosomes shorten
  and thicken (still in a pair)
• Centrioles move to the opposite poles of the cell
• At the poles, the centrioles send out spindle
  fibers
• Spindle fibers connect to the chromosomes at the
  centromere
• the nuclear membrane is broken down (can not
  see the nucleus)
• Same in Plant Cell except for the centrioles
  none in plant

6
Metaphase

• Chromosomes line up along cell equator (center of
  cell)
• Chromosomes begin to split away from duplicate
  (remember cell has 2 identical sets of
  chromosomes)

7
Anaphase

• Chromosomes are pulled apart by spindle fibers
• Half of the chromosomes go to one side toward one
  centriole and the other half go to the other
  centriole
• Spindle fibers seem to control the movement

8
Telophase

• Cell begins to divide
• Membrane between two groups of chromosomes - 2
  new cells are formed
• In an animal cell- called a cleavage furrow
• In a plant cell called a cell plate
• Nuclei form in the two cells with a nuclear
  membrane
• Chromosomes stretch out and get longer and
  thinner
• Result..2 daughter cells with an equal number of
  chromosomes as the parent

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Cytokinesis

• Cytoplasm divides into 2, so does the organelles
  in the cell

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Final Thoughts

• Mitosis takes place in most organisms
• More often in a new organism over an old organism
• WHY?
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